What
are noctilucent
clouds? Good question. They hover near
the edge of space, glowing
electric blue. Some
scientists think the clouds are seeded by space dust
and fed by rocket
exhaust. Others suspect they're a telltale
sign of global warming.
Whatever causes these mysterious clouds, they are lovely,
and summer is a good time to look
for them.Observing
tips: Although noctilucent clouds appear most
often at high latitudes--e.g. places like
Scandinavia and Canada--they have been sighted as far
south as Colorado, Utah and Virginia. Look west perhaps
30 minutes to an hour after sunset when the Sun has
dipped
6o to
16o below the horizon. If you see luminous
blue-white tendrils spreading across the sky, you've
probably spotted a noctilucent cloud.

Unless
otherwise stated, all
images are copyrighted by the photographers.

V. Petriew: "I
took 10 second exposures on my Olympus C-2100UZ every minute for 21
minutes and combined them in Paint Shop Pro's Animation Shop. The
first frame was taken at 2:41 AM CST on July 19th, 2003 and the last
frame was taken at 3:02 AM CST. Notice how the sky brightens during
that time period as we are still in perpetual twilight at 52 degrees
North Latitude until next week"

In some of these
photos, Lance Taylor managed to capture green auroras and pale blue
noctilucent clouds (NLCs) in the skies of Edmonton at the same time.
Note the contrast between the glowing NLCs and the dark ordinary clouds
in the
forground.

J. Koski: "It does not get
really dark here in the north, but a couple stars, the Moon, Mars
and
phenomena like these noctilucent clouds
can be seen during the few darkest hours.
I used a Canon EOS-D60
digital camera with a 20mm wide angle lens.
Exposure time was 2 seconds at f/2.8."

Anders Mørup-Petersen: "It was raining
heavily all evening, but as the sky started to clear up close to midnight,
it was easy to see that 'something was up.' Before I got out on the
countryside, the noctilucent cloud had dissolved a bit, but luckily,
heavy clouds were still covering the full moon to the south. Thse pictures
were taken with my Canon S30 at 8 seconds, aperture 2.8 with
iso 50 film. Notice the darker 'normal' clouds
at the horizon!"

Ian Kiming and Camilla
Bacher,
15 miles
south of Copenhagen, DenmarkJuly 12

R. Cockman: "Very
bright against the perpetual twilight, the display covered essentially
the entire northern half of the sky
to an altitude of 15deg; the variety of structures present and the noticable
change over timescales of minutes was breathtaking...the best I've ever
seen! As dawn approached the clouds became visible at elevations as high as
60deg. Even a casual observer couldn't help but see them! Images taken thru
a Nikon CoolPix 4500, 4sec exposures at effective speed of 400ASA.
"

S. Denfield: "Being
a casual observer of the night sky, this was the first time I have
knowingly seen these clouds. It was not a very large display, but it
caught my eye very directly and was beautiful to behold." Photo
details: Canon Powershot S45 digital camera, exposures unknown.